Thursday, January 29, 2015

No comment necessary

The Violence Policy Center put out a press release this morning relating gun ownership rates to gun death rates.  I wrote to them asking for the complete data, and plotted it.  Here is the plot.

In case you're interested, the bivariate regression's R-squared is .6.

Monday, January 26, 2015

Cities and the Environment--A first order effect?

I was reading a story about peak driving over the weekend.  In the course of reading the story, I discerned that we here in California drive far less than the average American.  In fact, California ranks 41st among the states in per capita driving:

Date are from the Insurance Institute for Highway Safety.

Given the stereotype about California (as a place where everyone drives, always), this was a surprise to me.  But then it dawned on me--when one excludes the District of Columbia (which is kind of like a state, just without representation), California is the most urbanized state in the country.  And so I drew a scatter plot of VMT per capita against urbanization by state:

The negative correlation is quite apparent. To anyone who might be interested, here is the bivariate regression:

       mpc |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
       var4 |  -81.73815    14.1223    -5.79   0.000     -110.118   -53.35832
       cons |   15994.33   1066.959    14.99   0.000      13850.2    18138.47

So a one percentage point increase in urbanization is associated with an 81 mile per year reduction in driving.  I think the direction of causality is not too big a problem here (it is hard to tell a story that more driving causes a reduction in urbanization).  So Matt Kahn, Ed Glaeser and Richard Florida are all right--cities are environmentally friendly!

[BTW, a little Googling led me to a paper that relates to all this].

Monday, January 19, 2015

How choosing the right discount rate matters to Max Scherzer

My student Hyojung Lee sent me to a cute article about how Max Scherzer's $210 million contract is not really a $210 million contract.  Because Scherzer is getting $15 million per year over 14 years, the present value of the contract is substantially less than $210 million; it is also worth less than a contract that pays $30 million per year over the seven years he is expected to pitch.

But Dave Cameron (the author of the piece) assigns a 7 percent discount rate to the contract.  The present value of $15 million per year over 14 years at a 7 percent discount rate is about $131 million. He chose 7 percent as the discount rate because that is the expected long run return of investing in the stock market.

A contract is not, however, like a stock.  It is a bond--contracts have seniority to equity, and guarantee a particular cash flow.  I would guess the Nats (unlike the Expos) are something like a BBB company.  The current bond yield on BBB issues is currently about 3.6 percent.  Discounting the value of the Scherzer contract at 3.6 percent produces a present value of $163 million.  Not that $131 million isn't nothing, but $163 million is a lot more.

[Update: Adam Levitin says that MLB teams are more like AAA (in bond rating, not playing quality, except, perhaps for the Diamondbacks last year), because all of baseball backs team contracts (when the Rangers went bankrupt, all players got paid).  That would drive the discount rate to 2.8 percent, and raise the value of the contract to $172 million.]